04 ATTACHMENT 1 - Laserfiche WebLink

Page: 1 Project and Location: Pleasanton Century House 'Orie2 Job No. 302.270-18 Scope: This calculation package- is intended to review and analyze the existing lateral force resisting system at the Pleasanton Century House to check -if the existing shear walls are adequate for seismic forces. Codes:: .. _ California Building Code (2016 CBC) ASCE-7-10 Design Criteria: The seismic parameters. for the site have been taken from the USGS seismic maps for seismic acceleration, the values are as follows:. . Ss = 1.8478 . S1.= 0.69g Sds = 1.2318 _ _ - Risk Category 11 The existing lateral force resisting -system of the Century House consists of a wood shearwall system with wood. siding and gypsum -board.: The -Code allows, for siding and gypsum board under ASCE 7-10, however the seismic base shear is significantly higher than a typical plywood shear wall system. The seismic base shear for analysis of the existing lateral system (wood siding/gyp) is: V=0.616 W. The seismic base shear for analysisof the proposed upgraded shear walls with plywood sheathing is: V=0.189 W. ..i Findings and"Recommendations: -Based on our analysis, the existing lateral force resisting system (shearwalls with wood siding and gypsum board) is not adequate to resist -the -Code forces. The allowable shear capacity of the shear walls is exceeded in each direction and on each floor of the building. Wesecommend adding plywood sheathing to the existing walls and holddowns. By adding the plywood sheathing, the base'shear "used -for analysis ;of the building, and thus the applied seismic loads, is reduced. Additionally, the plywood sheathing provides higher allowable shear capacities for the shear walls.